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Biology · chemistry of lifeBiological Molecules
Carbohydrates, lipids, proteins and nucleic acids are carbon-based molecules built from small units joined by removing water and split by adding it.
01 · The fourCarbs, lipids, proteins, nucleic acids
02 · Building blocksMonomers: sugar, amino acid, nucleotide
03 · Build and breakBuild = remove water; break = add water
01
What it is
4 macromolecules: carbohydrates, lipids, proteins, nucleic acids must know
Building blocks: sugars, amino acids, nucleotides; fats = glycerol + fatty acids must know
Carbohydrate jobs: quick energy (glucose) and structure (cellulose, chitin)
Lipids: nonpolar, don't dissolve in water — fats, phospholipids, steroids, waxes
Lipid jobs: long-term energy, insulation, membranes, steroid hormones
Protein jobs: enzymes, structure, transport (hemoglobin), hormones (insulin), antibodies
Heat or pH change denatures a protein — it loses shape and function
02
Parts & jobs
Carbohydrates: C, H, O in a 1:2:1 ratio (CH₂O)n — glucose C₆H₁₂O₆
Mono- (glucose) → di- (sucrose, lactose) → polysaccharides (starch, glycogen)
Fat (triglyceride) = glycerol + 3 fatty acids
Proteins = chains of 20 kinds of amino acids (polypeptides)
Nucleotide = 5-carbon sugar + phosphate + nitrogen base; DNA, RNA carry genes
03
Step by step
Dehydration synthesis builds (removes water); hydrolysis breaks (adds water)
04
The rules
Peptide bonds join amino acids; glycosidic bonds join sugars
05
Don't confuse
Glucose storage: starch in plants, glycogen in animals (liver, muscle)
Saturated: single bonds, solid (butter); unsaturated: double bond, liquid (oils)
06
Saturated or unsaturated fat?
Commonly confused | Saturated | Unsaturated |
|---|
| Carbon–carbon bonds | All single | At least one double |
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| Chain shape | Straight, packs tightly | Kinked |
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| At room temperature | Solid | Liquid (oils) |
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| Example | Butter, meat fat | Olive oil, canola oil |
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07
More detail
Show 6 more facts
Humans can't digest cellulose; cows need gut microbes to do it
Phospholipid: water-loving phosphate head, two water-fearing tails → bilayer
Steroids = 4 fused rings; cholesterol → steroid hormones, vitamin D
Amino acid = central C + NH₂ + COOH + H + R group (varies)
Primary structure = the amino acid sequence (1 of 4 levels)
Ester bonds hold fatty acids on glycerol; phosphodiester bonds link nucleotides
To build a macromolecule, take water out; to break one down, put water back in.
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